| Uwe Hermann | 5211a70 | 2010-09-27 17:53:17 +0000 | [diff] [blame] | 1 | /* |
| 2 | * This file is part of the coreboot project. |
| 3 | * |
| 4 | * Copyright (C) 2002 Eric Biederman <ebiederm@xmission.com> |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; version 2 of the License. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
| Uwe Hermann | 5211a70 | 2010-09-27 17:53:17 +0000 | [diff] [blame] | 14 | */ |
| Eric Biederman | fcd5ace | 2004-10-14 19:29:29 +0000 | [diff] [blame] | 15 | |
| Uwe Hermann | 5211a70 | 2010-09-27 17:53:17 +0000 | [diff] [blame] | 16 | __fpu_start: |
| 17 | /* Preserve BIST. */ |
| 18 | movl %eax, %ebp |
| 19 | |
| 20 | /* |
| 21 | * Clear the CR0[2] bit (the "Emulation" flag, EM). |
| 22 | * |
| 23 | * This indicates that the processor has an (internal or external) |
| 24 | * x87 FPU, i.e. floating point operations will be executed by the |
| 25 | * hardware (and not emulated in software). |
| 26 | * |
| 27 | * Additionally, if this bit is not cleared, MMX/SSE instructions won't |
| 28 | * work, i.e., they will trigger an invalid opcode exception (#UD). |
| 29 | */ |
| Eric Biederman | fcd5ace | 2004-10-14 19:29:29 +0000 | [diff] [blame] | 30 | movl %cr0, %eax |
| Uwe Hermann | 5211a70 | 2010-09-27 17:53:17 +0000 | [diff] [blame] | 31 | andl $~(1 << 2), %eax |
| Eric Biederman | fcd5ace | 2004-10-14 19:29:29 +0000 | [diff] [blame] | 32 | movl %eax, %cr0 |
| 33 | |
| Uwe Hermann | 5211a70 | 2010-09-27 17:53:17 +0000 | [diff] [blame] | 34 | /* Restore BIST. */ |
| 35 | movl %ebp, %eax |